Switch assembly for an airbag module attachment

ABSTRACT

A vehicle steering wheel assembly having a molded armature with outwardly extending spokes for mounting on a steering column. Airbag module engagement members extend from an airbag module housing to engage corresponding armature engagement members. The airbag module rests on a multiple of switch assemblies while the engagement members are separated by a clearance. The engagement members are only in contact if the airbag is fired. A clearance between each armature engagement member and each corresponding airbag module engagement member assures that there is no interference that may result in undesirable noise or vibration.

This is a Divisional of application Ser. No. 10/340,672, filed Jan. 13,2003, now U.S. Pat. No. 6,860,509 B2, which claimed priority ofprovisional application 60/355,494, filed Feb. 8, 2002.

BACKGROUND OF THE INVENTION

The present invention relates to an airbag module, and more particularlyto an attachment arrangement, which supports the airbag module upon aplurality of switches while providing primary airbag module retention.

It is well known to provide an airbag module in a vehicle at suchlocations as in a steering wheel, a dashboard, a seat, door panel orother location. A typical airbag module includes an airbag inflatorpositioned adjacent an airbag to discharge an inflator gas to inflatethe airbag upon sensing certain predetermined vehicle conditions.

The airbag module is commonly formed as a separate and independent unitfrom the vehicle. The airbag module must be easily installed yetdifficult to remove by an unauthorized person. Attachment of the airbagmodule is further complicated by the requirement that a horn actuator bemounted to the steering wheel assembly. Typically, the horn is triggeredby pressure applied to a portion of an airbag cover.

In one known arrangement, the airbag module is rigidly anchored to abase plate within a cavity formed by the molded armature of the steeringwheel assembly. A thin film actuator to activate a vehicle horn islocated between the airbag module and an airbag cover. Pressure appliedto the airbag cover triggers the thin film actuator to selectivelyactuate the horn. However, mounting of the airbag module is typicallywith threaded fasteners, which may complicate assembly and disassembly.Further, as the thin film actuator is mounted below the airbag cover andabove the airbag module, replacement of the actuator may be complicatedand time intensive should the thin film actuator fail.

In another known arrangement, a switch assembly is mounted to a baseplate within a cavity formed by the molded armature. The airbag moduleis then mounted to the switch assembly, such that pressure applied tothe airbag module moves the entire module and triggers the switch toactivate the horn. The switch assembly must be particularly robust tosupport the airbag module yet be able to restrain the airbag moduleduring airbag actuation. Disadvantageously, the robust design of theswitch assembly results in a complicated and expensive switch assembly.A driver must also apply a relatively large amount of pressure to movethe airbag module and trigger the switch. This may be ratherinconvenient.

Moreover, as the switch is located under the airbag module, enoughclearance must be provided to allow movement of the airbag modulerelative to the molded armature. Commonly, this results in a noticeableseparation line or gap between the airbag module and the steering wheelassembly. The separation line may be aesthetically displeasing and mayallow foreign objects to find their way between the airbag module andthe steering wheel assembly. The separation line may be furtherexaggerated by tolerance differences between the steering wheelassembly, airbag module and biasing member within the switch assembly.

Accordingly, it is desirable to provide an uncomplicated airbag mountingarrangement, which provides effective airbag module attachment. Theattachment should also allow convenient horn activation with minimalpressure. It is further desirable to minimize the separation linebetween the airbag module and the steering wheel assembly to provide anaesthetically pleasing steering wheel assembly.

SUMMARY OF THE INVENTION

Airbag module engagement members extend from an airbag module to engagecorresponding armature engagement members. The airbag module engagementmembers and the armature engagement members are preferably substantiallyhook shaped members. The airbag module rests on the switch assemblieswhile engagement members are separated by a clearance unless the airbagis deployed. The clearance assures that there is not interference, whichmay result in undesirable noise and/or vibration.

The switch assemblies engage the airbag cover and are located proximatethe steering wheel spokes and support the airbag cover which is attachedto the airbag module. One embodiment of the switch assembly includes afirst switch portion movable relative to a second switch portion. Thefirst switch portion includes a first switch engagement member of asubstantially hook shaped member which engages the airbag cover. Thesecond switch portion includes a second switch engagement member, whichfits within the.apertures formed within the molded armature. The switchassembly may thereby be “snapped” into the molded armature.

A biasing member such as a pair of coil springs mounted between thefirst switch portion and the second switch portion bias the first switchportion relative to the second switch portion. The airbag cover and theconnected airbag module rest upon the switch assemblies.

Another embodiment of a switch assembly includes a first switch portionmovable relative to a second switch portion while being biased by asingle biasing member.

Another embodiment provides a flexible electrical connection casing thatextends between a plurality of switch assemblies. A multiple of switchassemblies are molded as a single unit and connected to the vehicle horncircuit at a single connector.

Yet another embodiment of a switch assembly includes a first switchportion movable relative to a second switch portion while being biasedby a biasing member. The biasing member includes a flexible springplate, which also forms an integral first contact. The first contact ismovable relative a second contact mounted in the second switch portion.Still another embodiment of a switch assembly includes a first switchportion formed directly into the airbag cover. An uncomplicated andreliable switch assembly is thereby provided.

The present invention therefore provides an uncomplicated yet secureairbag mounting arrangement, which provides effective airbag moduleattachment.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention, which are believed to be novel,are set forth with particularity in the appended claims. The inventionmay be better understood by reference to the following description ofthe specific embodiments taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a general perspective view of a vehicle steering wheelassembly installed in a vehicle.

FIG. 2 is a partial sectional exploded view of a molded armature andsteering column.

FIG. 2A is a top view of a steering wheel armature illustrating amultiple of hook engagement members located at 3, 6 and 9 o'clockpositions.

FIG. 3 is an exploded view of a steering wheel assembly according to thepresent invention.

FIG. 3A is a bottom view of an airbag module illustrated in FIG. 3.

FIG. 3B is a perspective view of the steering wheel armatureillustrating a multiple of hook engagement members.

FIG. 3C is an exploded top view of the steering wheel assembly.

FIG. 3D is a perspective of an airbag housing illustrated in FIG. 3showing multiple engagement members for fastening the airbag housing tothe molded armature.

FIG. 3E is a perspective view of the airbag housing illustrated in FIG.3 D attached to the steering wheel armature shown in FIG. 3B.

FIG. 4 is a partial sectional view illustrating a switch assemblyaccording to the present invention.

FIG. 5A is a perspective view illustrating a step of mounting the airbagmodule to the steering wheel armature.

FIG. 5B is a sectional view from the 6 o'clock position of a steeringwheel assembly showing the airbag module mounted to the steering wheelarmature.

FIG. 6 is a bottom view of the steering wheel armature illustratingdisassembly apertures and also disassembly tool.

FIG. 6A is a sectional view at the 3'oclock position illustrating thedisassembly aperture of FIG. 6 and engagement members accessed thereby.

FIG. 6B is a bottom view illustrating a step of disassembling the airbagmodule from the molded armature.

FIG. 7 is an exploded view illustrating another switch assemblyaccording to the present invention.

FIG. 7A is a perspective view of a second switch portion of the switchassembly illustrated in FIG. 7 illustrating a switch contactarrangement.

FIG. 7B is a perspective view of the first and second contacts portionsof the switch assembly in FIG. 7.

FIG. 8A is a rear perspective view illustrating another switch assemblyaccording to the present invention.

FIG. 8B is a front perspective view of the switch assembly illustratedin FIG. 8A.

FIG. 9A is a perspective view illustrating another switch assemblyhaving two portions.

FIG. 9B is a perspective view of the switch assembly illustrated in FIG.9A.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a vehicle steering wheel assembly 10 positioned nextto the steering column 16. The steering wheel assembly 10 includes acentral hub portion 12 (FIG. 2A) with outwardly extending spokes 14. Thehub portion 12 has an axis 18 substantially perpendicular to the hubportion 12 and coaxial to the steering column 16. An essentiallycircular rim 20 is connected to the hub portion 12 by the spokes 14. Thespokes 14 are preferably arranged from the central hub portion 12 to therim 20 at 90, 180 and 270-degree positions. In other words, the spokes14 are arranged at 3, 6, and 9 o'clock positions where 12 o'clock is thetop of the rim 20 when viewed from the driver's position. One skilled inthe art appreciates that the steering wheel assembly 10 could have anynumber of spokes and the spokes could be arranged in differentpositions.

Referring to FIG. 2, the steering wheel assembly 10 includes a metallicsteering wheel armature 30, which is overmolded with a non-metallicmaterial 32 such as polyurethane material or the like to form what isreferred to as a “molded armature” . The hub portion 12 is preferablysecured to the steering column 16 by a threaded fastener 34 such as abolt or the like. The fastener 34 engages corresponding threads 36within the steering column 16. One skilled in the art appreciates thatother fastening arrangements are suitable for the present invention. Thenon-metallic material 32 defines the essentially circular rim 20 andspokes 14 about the hub portion 12 and forms a cavity 38 to receive theairbag module 22.

Referring to FIG. 3, an exploded view of the steering wheel assembly 10is illustrated. The airbag module 22 is mountable within the cavity 38and concealed by the airbag cover 24. When a driver exerts pressure onthe airbag cover 24, at least one switch assembly 26 is closed. Eachswitch assembly 26 activates a horn (not shown) in a known manner. Asthe switch assemblies 26 are preferably located proximate the airbagcover 24, minimum pressure is required to activate the horn. Although aparticular steering wheel assembly 10 having a particular spoke hub andrim design is illustrated in the disclosed embodiment, it should berealized that other steering wheel assemblies will benefit from thepresent invention.

As shown in FIG. 3, the airbag cover 24 includes attachment members 40,which fixedly engage an airbag housing 21. The attachment members 40include apertures 42, which receive corresponding tabs 44 (FIG. 3D)extending from the airbag housing 21. It is understood that the airbagcover 24 can be attached the airbag housing by other arrangements. Aninflator 46 is located within the cavity 38 and provides inflation gasto an airbag 48 during a car crash. An electrical connector 50 (FIG. 3A)extends from the inflator 46 and is connectable to an airbag firingcircuit (illustrated schematically at 51).

Airbag module engagement members 52 (illustrated in FIG. 3D) extend fromthe airbag housing 21. armature engagement members 54 (illustrated inFIG. 3B) corresponding to the airbag module engagement members 52 extendfrom the hub portion 12 of the armature. Preferably, the airbag moduleengagement members 52 and the armature engagement members 54 aresubstantially hook shaped members (FIG. 3). As will be further describedbelow, the airbag module 22 rests on the switch assemblies 26 whileengagement members 52, 54 are normally separated by a clearance C (FIG.3E) and are only in contact, if the airbag 48 is deployed.

Referring to FIG. 3A, the airbag cover 24 includes a plurality of switchassembly receivers 56. The receivers 56 each include an airbag coverengagement member 58 such as a substantially hook shaped engagementmember to engage the switch assemblies 26 (FIG. 4).

Referring to FIG. 3C, the switch assemblies 26 are preferably locatedproximate each spoke 14 and support the airbag cover 24. The switchassemblies 26 are mounted within apertures 60 formed within the moldedarmature 32. The airbag cover 24 is mounted to the airbag module 22 andis mounted in a close fitting relationship with the molded armature 32.The switch assemblies 26 directly engage the airbag cover 24 receivers56 (FIG. 3A) which are located proximate the spokes 14. The componenttolerance stack up is thereby minimized. Moreover, an aestheticallypleasing fit between the airbag cover 24 and the molded armature 32 isprovided which minimizes any separation line while still allowing hornactivation by allowing movement of the airbag cover 24 relative to themolded armature 32.

Referring to FIG. 4, one embodiment of a switch assembly 26 isillustrated in a mounted position. The switch assembly includes a firstswitch portion 62 movable relative to a second switch portion 64. Thefirst switch portion 62 includes a first switch engagement member 66preferably including a substantially hook shaped member which engagesthe switch assembly receiver 56 having corresponding engagement members58. The airbag module 22 is “snapped” onto the first switch portion 62.However, other mounting arrangements may alternatively or additionallybe provided.

The second switch portion 64 includes engagement members 70, which fitwithin the apertures 60 formed in the molded armature 32. The secondswitch engagement member 70 is preferably of a substantially cylindricaldesign having a ramped locking shoulder 72, which is engageable with ashoulder 74 formed by an enlarged diameter 76 within the aperture 60.The switch assembly 26 is also preferably “snapped” into the moldedarmature 32.

A biasing member 78 mounted between the first switch portion 62 and thesecond switch portion 64 biases the first switch portion 62 relative tothe second switch portion 64. In the embodiment of FIG. 4, the biasingmember 78 is a coil spring which forces (illustrated as double headedarrow F) the first switch portion 62 away from the second switch portion64. The switch assemblies 26 support the airbag cover 24 and theconnected airbag module 22.

The first switch portion 62 further includes a first hook 80 and thesecond switch portion 64 includes a second hook 82. The hooks 80,82interact under the force of the biasing member 78, to limit movement ofthe first switch portion 62 relative to the second switch portion 64.Although the hooks 80,82 are illustrated as corresponding hook shapedmembers in the disclosed embodiment, it should be understood that otherhooks which limit relative movement of the switch portions 62,64 mayadditionally or alternatively be provided.

A first contact 84 mounted to the first switch portion 62 is therebymovable relative to a second contact 86 mounted on the second switchportion 64. By pressing on the airbag cover 24, the first switch portion62 is moved in the direction of arrow H toward the second switch portion64 such that the first contact 84 will touch the second contact 86. Acircuit (illustrated by electrical connectors 88 a and 88 b) is closedand the horn 28 is activated.

A method for installing the above mentioned airbag module 22 within amolded armature 32 will now be described. However, it should be realizedthat the use of a steering wheel is for illustrative purposes only, andthat the methodology of the present invention may be applied to othercomponents.

Referring to FIG. 5A, the molded armature 32 is first secured to thesteering column 16 by the threaded fastener 34 (FIG. 2). The switchassemblies 26 are then mounted within the apertures 60 formed within themolded armature 32. The switch assemblies 26 preferably just “snap” intoplace (FIG. 2A). A wiring harness (88A and 88B) for the horn is thenconnected to the switch assemblies 26.

Referring to FIG. 5A, the airbag cover 24 has been previously attachedto the airbag housing 21 with the attachment member 40 to form theairbag module 22. The electrical connector 50 of the inflator 46 isconnected to the airbag firing circuit 51 (also illustrated in FIG. 3A).The airbag module 22 is then located within the cavity 38 of the moldedarmature.

Preferably, the airbag module engagement member 52′ located at the 6o'clock position is first aligned with the armature engagement member54′ located at the 6 o'clock position (FIG. 3E). The airbag module 22 istipped toward the armature engagement member 54′, preferably atapproximately 10 degrees below axis 19 (FIG. 1). Axis 19 isperpendicular to axis 18. The airbag module engagement member 52′ isengaged with the corresponding armature engagement member 54′ and theswitch assembly 26 located at the 6 o'clock position is aligned with theswitch assembly receiver 56 within the airbag cover 24 (FIG. 3E). Theairbag module 22 is then tipped toward axis 19 such that all of thefirst switch engagement members 66 are aligned with their correspondingairbag cover engagement members 58.

The operator then simply presses against on the airbag cover 24proximate the spokes 14 within the airbag cover 24 until each firstswitch engagement member 66 engages their corresponding airbag coverengagement members 58 within the airbag cover 24. The armatureengagement members 54 and the airbag module engagement members 52 arealso engaged at this time. In other words, the airbag module 22 is“snapped” onto the switch assemblies 26 which have been previously“snapped” into the molded armature 32. An uncomplicated yet secureattachment arrangement is thereby provided by the present invention.

Referring to FIG. 5B, a clearance C is formed between each armatureengagement members 54 and the corresponding airbag module engagementmembers 52 when the module 22 is mounted to the molded armature 32. Themodule 22 thus rests on the switch assembly 26. Preferably, theclearance C is approximately 1 mm. The clearance C assures that there isnormally no interference between each armature engagement member 54 andthe corresponding airbag module engagement members 52 which may resultin undesirable noise and or vibration.

To activate the horn (FIG. 1), a driver need only press on the airbagcover 24 and overcome the biasing members 78 such that the first contact84 touches the second contact 86 (FIG. 4). It should be understood thatwhen the driver presses on the airbag cover 24, the clearance C willslightly increase. Although there is normally a clearance C, theclearance C will be eliminated during deployment of the airbag. In otherwords, when the airbag is fired, each armature engagement member 54 willengage each corresponding airbag module engagement member 52 to providea rigid attachment between the airbag module 22 and the molded armature32. In this way, the switch assemblies 26 need not provide airbag moduleretention during airbag deployment.

Referring to FIG. 6, a disassembly aperture 89 is located through thearmature 30 preferably adjacent the 3 o'clock and 9 o'clock armatureengagement member 54 (FIG. 2A). To provide an additional anti-theftfeature, the disassembly apertures 89 may be located relative to thesteering column 16 (FIG. 1) and under the steering wheel assembly 10such that the steering wheel assembly 10 must be rotated to a predefinedposition to access the apertures 89.

Referring to FIG. 6A, a sectional view of the steering wheel assembly 10illustrates a method of disassembly. A flat bladed disassembly tool 53is receivable through the disassembly aperture 89 (FIG. 6B). The tool 53is inserted between the armature engagement member 54 and thecorresponding airbag module engagement member 52. The tool 53 is thenrotated to spread the airbag module engagement member 52 away from thearmature engagement member 54. The module 22 is then lifted to assuredisengagement between the armature engagement member 54 andcorresponding airbag module engagement member 52. The tool 53 can thenbe inserted into the other disassembly apertures 89 and the processrepeated. The airbag module 22 is tilted and lifted away from the moldedarmature 32 to disassemble the steering wheel assembly 10 in the reverseorder of assembly as described above.

Referring to FIG. 7, another embodiment of a switch assembly 26A isillustrated. The switch assembly 26A includes a first switch portion 90movable relative to a second switch portion 92 while being biased by asingle biasing member 94. The first switch portion 90 and second switchportion 92 are engaged together and mounted to the airbag cover 24 andthe molded armature 32 essentially as described above.

A first contact 95 mounted to the first switch portion 90 is movablerelative to a second contact 96 mounted on the second switch portion 92.By pressing on the airbag cover 24, the first switch portion 90 is movedin the direction of arrow H toward the second switch portion 92 suchthat the first contact 95 will touch the second contact 96. A pair ofalignment pins 101 further extend from the first switch portion 90. Thepins 101 are movable received within alignment apertures 103 formed inthe second switch portion 92. The alignment pins 101 and alignmentapertures 103 further assure that the airbag cover is stabilized andpressure thereon will be more directly exerted upon the switch assembly26 a. A flexible casing 98 extends from the second switch portion 92such that a plurality of switch assemblies 26 can be molded as a singleunit (FIG. 7B) with a single circuit connection.

The first contact 95 is integral to the coil spring which forms thebiasing number 94 as illustrated in FIGS. 7, 7A and 7B. Installation isthereby simplified as a multiple of switch assemblies can be installedand connected in parallel, although only a single connection need bemade. Referring to FIG. 7A the flexible casing 98 includes a firstelectrical connection 100, which is electrically connected to the firstcontact 95 through the biasing member 94. The flexible casing 98 furthercontains a second electrical connection 102, which is insulated from thefirst connection 100 by the flexible casing 98. The second electricalconnection 102 is electrically connected to the second contact 96mounted on the second switch portion 92.

By pressing on the airbag cover 24 (FIG. 7), the first switch portion 90is moved in the direction of arrow H such that a circuit is closed andthe horn 28 is activated. Referring to FIG. 7B, the closed circuit isformed from the first electrical connection 100, through the biasingmember 94, to the first contact 95, to the second contact 96 and back tothe second electrical connection 102.

Referring to FIG. 8A, another embodiment of a switch assembly 26B isillustrated. The switch assembly 26B includes a first switch portion 104movable relative to a second switch portion 106 while being biased by abiasing member 108. A fastener 105 extends from the biasing member 108to mount the biasing member 108 to the second switch portion 106. Aguide pin 107 which extends from the first switch portion 104 ispreferably movable within the fastener 105 such that the first switchportion 104 is movable relative to the second switch portion 106. Itshould be understood that although a particular mounting arrangement isillustrated other mounting arrangements are contemplated which provideengagement of the biasing member 108 and relative movement between thefirst and second switch portions 104,106. The switch assembly 26B ismounted to the airbag cover 24 and the molded armature 32 essentially asdescribed above.

Referring to FIG. 8B, the biasing member 108 includes a flexible springplate 109 which also forms an integral first contact 110. The firstcontact 110 is movable relative to a second contact 112 mounted in thesecond switch portion 106. The biasing member 108 includes a flexiblecasing 114 as described above. By pressing on the airbag cover 24, thefirst switch portion 104 overcomes the bias of spring plate 109 suchthat the integral first contact 110 is moved in the direction of arrow Hto touch the second contact 112 and close the circuit, wherebyactivating the horn.

Referring to FIG. 9A, another embodiment of a switch assembly 26C isillustrated. The switch assembly 26 c includes a first switch portion116 formed into the airbag cover 24 to further minimize part count andcomplexity. A second switch portion 118 mounts a biasing member 120,essentially as described above. A fastener 122 extends from the biasingmember 120 to mount the biasing member 120 to the second switch portion118.

Referring to FIG. 9B, a guide pin 123 extends from the first switchportion 116 and passes through the fastener 122 such that the firstswitch portion 116 is movable relative to the second switch portion 118.An actuator 125 extends from the first switch portion 116 to actuate aflexible spring plate 128 essentially as described above.

The biasing member 120 mounted between the first switch portion 116 andthe second switch portion 118 biases the first switch portion 116relative to the second switch portion 118 as described in the previousembodiment. Notably, a flexible casing 98′ as described above extendsfrom the biasing member such that a plurality of switch assemblies 26 cmay also be molded as a single unit (FIG. 7 b).

The first switch portion 116 includes a first hook 124 and the secondswitch portion 118 includes a second hook 126. The hooks 124,126interact to limit movement of the first switch portion 116 relative tothe second switch portion 118. Although hooks are shown in the Figures,it should be understood that other shaped members which limit movementof the switch portions 124,126 may additionally or alternatively beprovided.

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A snap-in switch assembly comprising: a first switch portion mountinga first contact; a first switch engagement member extending from saidfirst switch portion engageable with an airbag cover wherein said firstengagement member includes one or more substantially hook shapedengagement members snap-in engageable with one or more substantiallyhook shaped members extending from the airbag cover; a second switchportion, said second switch portion mounting a second contactcorresponding to said first contact; and a second switch engagementmember extending from said second switch portion engageable with ametallic steering wheel armature that is overmolded with a non-metallicmaterial, wherein said second switch engagement member includes one ormore substantially cylindrical shaped engagement members having anextended portion, said one or more substantially cylindrical shapedengagement members snap-in engageable with one or more apertures definedby the overmolded steering wheel armature wherein said first switchportion is movable relative to said second switch portion, said firstswitch portion includes one or more first hooks and said second switchportion includes one or more second hooks, said first and second hookssnap-in engage when said airbag cover is attached to said overmoldedsteering wheel armature and interact to limit movement of said firstswitch portion relative to said second switch portion.
 2. The switchassembly according to claim 1 further comprising a biasing member tobias said first switch portion relative to said second switch portion.3. The switch assembly according to claim 2 wherein said biasing memberincludes a coil spring.